Trifluoroacetyl chloride is a known commercially useful compound that can be used to synthesize important industrial products. For example, it can be hydrolyzed according to known techniques to obtain trifluoroacetic acid which then can be used either as a dimerization catalyst of unsaturated aliphatic hydrocarbons in the production of pharmaceutical products or as the active ingredient in pesticide formulations.
It is known that trifluoroacetyl chloride can be synthesized by noncatalytic processes. French Pat. No. 2,226,380 describes the synthesis of trifluoroacetyl chloride by subjecting 1,1-dichlorotrifluoroethane and oxygen in the gaseous phase to ultraviolet radiation. This process requires extensive safety measures to avoid the danger of explosion, highly complex photochemical equipment, and large amounts of light and caloric energy. In addition to these drawbacks, the process produces a relatively low yield of trifluoroacetyl chloride.
French Pat. No. 1,385,111 discloses a process for photochemical chlorination of pure liquid fluoral at about -30.degree. C. in the presence of ultraviolet light. This method cannot be used commercially because fluoral polymerizes so rapidly that storage of this material is difficult. Also, the process of the French patent does not provide a satisfactory reaction rate or a sufficiently high yield.
It is also known that trifluoracetyl chloride can be synthesized catalytically from compounds other than fluoral. For example, French Pat. No. 2,038,257 describes the catalytic oxidation of 1,1,1-trichlorotrifluoroethane with sulfur trioxide. This process has two disadvantages; the use of toxic catalysts with a mercuric sulfate base and the formation of a troublesome sulfuryl chloride byproduct.
French Pat. No. 2,169,221 relates to a process for preparing trifluoroacetic acid, one step of which consists of catalytically transforming trifluoroacetyl fluoride into trifluoroacetyl chloride in the presence of carbon tetrachloride, chloroform, or trichlorofluoro methane. This method has the disadvantage of inevitably forming byproducts such as, for example, trichlorofluoro methane when carbon tetrachloride is used.